What are the 'N' and 'S' signs in the 'A Roadside Stand' by Robert Frost?

Question

I read the poem "A Roadside Stand" by Robert Frost. I am confused by the reference to "N" and "S" signs in tree poem. What do those signs refer to?

The little old house was out with a little new shed
In front at the edge of the road where the traffic sped,
A roadside stand that too pathetically pled,
It would not be fair to say for a dole of bread,
But for some of the money, the cash, whose flow supports
The flower of cities from sinking and withering faint.
The polished traffic passed with a mind ahead,
Or if ever aside a moment, the out of sorts
At having the landscape marred with the artless paint
Of signs that with the N turned wrong and S turned wrong
Offered for sale wild berries in wooden quarts,
Or crook-necked golden squash with silver warts,
or beauty rest in a beautiful mountain scene,
You have the money, but if you want to be mean,
Why keep your money (this crossly) and go along.
The hurt to the scenery wouldn't be my complaint

I have read somewhere that these are the direction signs for north and south. But I personally think that these are the letters on the seller's shop which actually are in the name of the shop. I think so because the writer says that, these signs offered wild berries for sale. If it were the direction signs, the writer won't have said that.

Answer 1

"N" and "S" are letters that are frequently mistakenly written backwards by children, and others of a low level of literacy. For that reason, if written on backwards on a sign they denote a barely literate writer.

Sometimes letters are deliberately reversed to give a "folksy" touch to a piece of writing, but in this case, Frost explicitly calls them "artless" mistakes.

It all goes along with the poem's larger theme of poor country people who are despised and ignored by the wealthier, more sophisticated urbanites.